Pulp molding apparatus utilizing multiple vat chambers



Feb. 1, 1966 J. E. FOOTE ETAL 3,232,827

PULP MOLDLNG APPARATUS UTILIZING MULTIPLE VAT CHAMBERS Filed Nov. 4,1964 INVENTORS JAMES E. FOOTE ROGER WELLS ATTORNEY United States Patent3,232,827 PULP MOLDENG APPARATUS UTEIZING MULTIPLE VAT HAMBERS James E.Foote, Westport, and Roger Wells, Stamford,

Comm, assignors to Diamond International Corporation, a corporation ofDelaware Filed Nov. 4, 1964, Ser. No. 408,899 14 Claims. (Cl. 162-228)The present application is a continuation-impart of application SerialNo. 191,985 of James E. Foote, filed May 2, 1962, now patent No.3,165,437.

The present invention relates to an improved pulp molding apparatus, andmore particularly to an apparatus for forming molded pulp articlesutilizing multiple vat chambers.

The use of molded pulp articles, such as meat trays, egg cartons, flowerpots, etc, has become quite universal, generally because of the throwaway character of the articles, ease in manufacture, relatively lowcost, and the rapid rate and simplicity by which similar articles can beuniformly produced.

There is a constant endeavor in the industry to maintain the quality ofthe articles at a maximum, this generally being afforded by theconsistency of the molding material used and the degree to which moldingconditions can be controlled during article production. Many molded pulparticles, when mass produced, must be rejccted as imperfect due toexcessive warpage, excessively thinned out sections, variation in weightalong the length of the products, etc. Many of these problems, partiularly a lack of uniformity iri weight of the articles along theirlength, are generally due to a lack of homogeneity of the articleproducing fibers in the pulp slurry; this lack of homogeneity is due toeddy currents in the pulp stock slurry. Other causes of lack ofuniformity are due to the washing away of the pulp preform on thesuction molds after deposition, the running of lightly held gelatinouspulp toward the trailing end of the dies as the dies leave the pulpslurry, etc.

Many attempts have been made in the prior art to overcome the problemsof excessive warpage and lack of uniformity, but these have not alwaysbeen entirely successful from the standpoint of either accomplishing ofdesired result or being sufliciently inexpensive, partly because some ofthe causes of warpage and lack of thickness regularity have not beenknown. The above mentioned application of James E. Foote has provided afirst practical success in accomplishing the above ends.

It is, therefore, an object of the present invention to provide animprovement of the invention of James E. Foote, mentioned above, anddescribed in application Serial No. 191,985 and filed May 2, 1962.

It is another object of the present invention to overcome the problemsof the prior art, such as indicated above.

It is another object of the present invention to provide a new andimproved apparatus for producing uniform pulp molded articles.

It is another object of the present invention to provide a uniform andconsistent pulp slurry where the pulp fibers therein are uniformlyconsistent and properly oriented in a substantially undisturbedcondition so that articles may be produced in controlled conditionswithout loss of time, excessive rejects, and without substantialmodification of presently available equipment.

It is another object of the present invention to provide an apparatuswhich will prevent lightly held gelatinous pulp from running down towardthe trailing end of a pulp molded article.

It is another object of the present invention to provide a pulp stockslurry in constant movement within a slurry tank to obviate flocculationand channelling so that a suction die in contact with the pulp stockslurry contacts a relatively homogeneous mass without material fiberdisorientation or washing of the pulp preforms forming on the suctiondies.

It is another object of the present invention to provide a relativelysimple, inexpensive and highly effective apps.- ratus for accomplishingthe above objects.

Other objects and the nature and advantages of the instant inventionwill be apparent from the following description of an exemplaryembodiment of the invention taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a sectional side elevation, partly schematic, of oneembodiment of an apparatus in accordance with the present invention;

FIG. 2 is a view, similar to FIG. 1, showing a preferred embodiment ofthe present invention;

FIGS. 3 and 4 are sectional views, partly schematic, showing a detail ofthe general apparatus of FIG. 2 as other embodiments; and

FIG. 5 is a partly schematic, broken away, sectional view taken in aplane perpendicular to the planes of FIGS. 14 through a typical suctiondie and showing two embodiments of requisite attaching means.

Referring to the drawings in detail, wherein like reference charactersare used to designate like or corresponding parts throughout the severalviews, there is shown in FIG. 1 a suitable suction die carrier generallyat ll), which preferably takes the form of a revolving molding drum 12which may rotate continuously or intermittently about its axis 13. Thedrum 12 has a plurality of suction molding dies 14 spaced peripherallythereabout and connected via hollow spokes to a source of vacuum as iswell known in the art. A curved molding vat shown generally at 16 isprovided in essentially complenemtary facing relationship to the drum12. The vat 16 is provided with suitable bottom and side Walls,described below, and is adapted to contain a fibrous pulp stock slurry.A stock entrance 18, a vat discharge exit 2t) and an overflow exit 22are provided for the vat 16. A circulating pump 24 (note FIG. 2) isprovided to recirculate pulp stock between the exits 2t) and 22 and theentrance 18.

At the discharge or exit end 20 of the vat 16 is provided a stockreservoir 26 into which a suit-able supply of pulp stock slurry isintroduced; the reservoir 26 communicates with an inlet conduit 28connected to the circulating pump 24. The pump 24 communicates with anoutlet conduit -39 having a valve 32 therein and the conduit 30 isconnected to the stock inlet 18. The overfiow exit 22 is, in turn,connected via a suitable conduit 34 to the recirculating system at apoint upstream from the circulating pump 24, such as by connecting thepipe 34 to the reservoir 26, as shown in FIG. 2. Stock as needed may beadmitted to the reservoir 26 via a pipe 3d; similarly, white Water maybe added to the system via a pipe 38.

The reservoir 26 may be more or less frusto conical as shown in FIG. 1,or it may have a more complex shape, as shown in FIG. 2. In FIG. 2, thereservoir 26 comprises a more or less conical chamber 261 with a bafile262 extending radially thereacross. Directly below t-he baffie .262 isan outlet 263 for the conduit 28. Inaddition, a conical sub-chamber 264may be provided adjacent and connected to the chamber 261 for admissionof white water via the pipe 38.

A primary chamber $2 is provided in the vat 16 above the inlet 18 andwithin the primary chamber 42 directly above the inlet 18 is provided asuitable baflle 40 for breaking the direction of flow of the stockslurry arriving from the conduit 30. The level of the pump stock J!slurry within the vat 16 is maintained at least as high as the top of aseparator 44 dividing the overflow outlet 22 from the vat 16.

The rate of circulation of the pulp stock slurry will be suflicient toprevent the channelling and flocculation of the stock which is essentialin order to produce pulp articles of a uniform quality. Part of thestock will circulate through the vat 16 into the overflow exit 22 andpart will circulate from the primary chamber 42 of the vat into asecondary chamber 46 of the vat and then to the discharge exit 20.

The vat 16 of the present invention is relatively complex in structurecompared to anything known in the prior art and is formed from aplurality of walls which separate the vat 16 into the primary chamber 42and the secondary chamber 46.

In the embodiment of FIG. 1, the primary chamber 42 is defined by anouter wall 48 and requisite side walls (not shown). Separating theprimary chamber 42 from the secondary chamber 46 is a false bottom wall50 which extends laterally across the entire width of the vat 16. Thelength of the false bottom 50 is preferably equal in length to twoprocess steps during the rotation of the drum 12, i.e., the wall 50should be of such a length so that two suction dies 14 are disposed overit during rotation of the drum 12 (as shown in FIG. 1). Either a slot ora lateral row of holes 52 is provided across the width of the falsebottom 50 to provide communication between the secondary chamber 46 andthe primary chamber 42.

In the embodiment of FIG. 2, a wall 54 delineates the bottom surface ofthe primary chamber 42. Two false bottom walls 56 and 58 separate theprimary chamber 42 from the secondary chamber 46. The wall 56 is highlyperforated to permit flow of pulp therethrough while the wall 58 isimperforate.

wall 60 of the secondary chamber at about /2 way along its lengththereof.

A critical aspect of the present invention is the relationship betweenthe location of the discharge exit and the force of pulp slurry infeedto the secondary chamber 46. The apparatus should operate so that thedifference between the force of infeed and the static head of slurrydownstream from the lowermost point of travel (step 3) of each die 14due to any elevation of the discharge exit 20 above the infeed point issutficient to maintain a net flow of slurry past the dies 14 in adirection the same as their direction of travel. In most instances, asshown in FIGS. 1-4, the discharge exit 20 will therefore be locatedapproximately at a point adjacent and only slightly downstream from theextreme downward position of the dies 14. Noting the numbered steps inFIGS. 1 and 2, the dies 14 leave the surface of the stock in thesecondary chamber 46 after step 3. In normal molding procedures, themold leaves the surface of the stock in the vat after steps 4 or 5; asthe molds leave the stock in the upward direction, the last formed andlightly held gelatinous pulp has a tendency to run down toward thetrailing edge of the pulp deposit and this causes the trailing edge ofthe item produced to be thicker than the leading edge and also causesthe pulp to cling to the lip of the trailing edge which providesfeathery edges of pulp fibers on the article which must be washed offwith deckle showers. With the discharge exit 20 located immediatelyafter step 3, at a point adjacent the extreme downward position oftravel of each die 14, the stock falls away from the mold in ahorizontal plane as the mold advances from step 3 toward step 4, andthis reduces the deposition of extra stock on the trailing edge of thearticle produced and also reduces the formation of feathery edges ofpulp fibers sufficiently to eliminate the need for deckle showers,

In the vat embodiments 16 of both FIGS. 1 and 2, the provision ofbaflles 41), holes (such as those in wall 56 or holes 52), and theby-pass section 62, all combine to reduce the rate of movement ofvelocity of stock in the secondary chamber 46 to a level significantlylower than the velocity of pulp in the primary chamber 42; eddy currentsand washing of a deposited pulp preform is thereby maintained at aminimum.

Any desired form of die 14 or die carrier 12 can be utilized, and inthis exemplary embodiment, there is disclosed the rotary type whichincludes a transverse supporting shaft 13 defining the axis ofgeneration of the curvature of the walls or 60. The shaft 13 extendsthrough a suction manifold communicating through a plurality of radiallyextending suction lines to the circumferentially spaced suction molddies 14 mounted on the outer rim of the die carrier 12, in a manner wellknown in the art.

As is conventional in the art, a negative pressure vacuum will beintermittently communicated through suitable valve mechanisms (notshown) to the suction mold dies 14 when they are introduced into thepulp stock slurry vat 16. Accordingly, when suction is applied at theexposed effective surface of the suction mold dies 14, a pulp preformwill be deposited on the outer surface of the suction mold dies 14. Thedies 14 will be continuously or intermittently (stepwise) moved throughthe vat 16 and especially the secondary chamber 46 thereof in the mannerindicated by the direction arrow in FIGS. 1 and 2; stock deposition onthe effective surface of the suction dies 14 will be, for the most part,in the secondary chamber 46 in which the stock slurry moves at a lowvelocity.

Extending transversely between each pair of dies 14 and extendingradially from the die carrier 12 are wiper blade elements 64, preferablyof the type described in copending application Serial No. 301,371, filedAugust 12, 1963, in the name of Roger Wells. If desired, wiper blades ofthe type described in parent application Serial No. 191,985 and calledscraper or pusher bars may also be used. The wiper blades 64 includes afree lower edge 66 which contacts and rubs against the secondary chamberforming Walls 50 (FIG. 1) and (FIG. 2). The free end 66 of the Wiperblade 64 effect a sealing or contacting relation with the secondarychamber forming walls 50 and 60. The wiper blades 64 each form forwardlythereof accumulator chambers when the free ends contact the wiper bladecontacting walls 50 or 60, which accumulator chambers maintain arelatively quiescent zone of pulp stock slurry therein which slurry isrelatively homogenous, well mixed and moving at a relatively low rate.

Thus the combined effect of baflies, holes between chambers, and bypasssections, together with the wiper blades 64, give a quieting effect tothe stock as it is molded during critical periods. In addition, thecreation of eddy currents and washing of the deposited pulp preform isminimized. The wiper blades between each molding die serve to trap thestock and dampen out eddy currents, which eddy currents can causevariation in weights and the various items mounted on the individualmolding dies. In addition, as the molding wheel steps, the wiper bladesforce the trapped stock to move in unison with the molds. Thissubstantially reduces irregular washing of the molded articles andproduces an article with a much more uniform distribution over itsentire area.

The purpose of the transverse holes 52 in the false bottom 50 of theembodiment of FIG. 1 is to introduce stock to the accumulator chamber atstep 3. Further holes are not provided because when stock slurry isprovided for a particular step (e.g. steps 2 or 3) it is desirable tomaintain the slurry in a quiescent state and further holes would have acontrary effect.

The embodiment of FIG. 2 is preferred because the use of a bypasssection 62, causing the pulp in step 3 to be received solely from thatnot used during step 2, reduces washing of the pulp deposit, i.e. thebypass causes less washing of the article than stock entering throughholes in the false bottom. In an intermittently operating machine, thewiper blades 64 are in position shown in FIG. 2 about 56% of the time.

It may be desirable in certain situations to utilize dilution waterjetting means such as a row of transversely located spray pipes 68 or68. In the embodiment of FIG. 2 the spray pipes are shown in twoalternate positions, either one of which may be used; thus spray pipes68 may be positioned in the primary chamber 42 between the baflie 40 andthe perforated false bottom 56, or the spray pipes 68 may be positionedin the secondary chamber 46 between the false bottom 56 and the wiperblade contacting wall portion 60. The purpose of such pipes 6t}v or 68'is to provide diluting water to reduce the consistency of the stock, toreduce the weight of the articles directly downstream from the dilutionoutlets. With the improved control due to the provision of the wiperblades and the secondary chamber, the improved controlled stock flow maybe further effectively controlled by such dilution means.

Another item which may be used in the present invention, particularlythe embodiment shown in FIG. 2, is the. utilization of a shielding meanscomprising a laterally extending plate 70. The shielding plate 70prevents pulp deposit formation during step 1. This makes it possibleto. increase the static head and depth of the stock in the vat. Althoughincreasing the static head improves forrnation to some extent, the useof such a shielding plate 70 may not always be desired when extramolding time is more desirable, i.e. extra molding time is offered byhaving step 1 under vacuum.

FIG. 4 shows another device which may be utilized in the presentinvention, and more particularly in the embodiment of FIG. 2. In thiscase the secondary chamber forming wall 60' is periodically made shorterthan twice the distance between wiper blades 64-. In this embodiment ahinge 72 is provided between the wall 66 and an extension thereof 74. Acam 76 and suitable linkage 78 is associated with the bottom extension74 and the rotation of the cam 76 periodically moves the extension 74about the hinge 72 to dump the stock from between the blades 64 at step3. The purpose of this is to permit a flow of stock across thestationary mold during intermittent operation to wash the bottom of thepulp deposit thin without reducing the wall thickness. For a givenweight article the wall strength can be increased at the expense of thebottom.

This hinge need not be operated intermittently. Thus in FIG. 3 the wall60 may be so formed with a dip 89 so as to give a continuous flow instep 3 to achieve the desired washing characteristics. Similarly theextension 74 in FIG. 4 may be adjusted about the hinge 72 to be opened afixed amount without rotation of the cam 76 to provide the same results.

As described in copending application Serial No. 301,371, it isdesirable in the present apparatus to provide some sealing arrangementat the sides of the drum and, thus, side skirts may be utilized as shownin copending application Serial No. 391,371. Otherwise, side sealingarrangements such as shown in FIG. 5 may be utilized. Side skirts $2 maybe attached directly to the drum 12 at its peripheral edges 84 via abolt 86. A filler piece 88 may be provided between the edge 84 and theskirt 82. The purpose of the side skirts is to prevent slurry fromflowing behind the dies 14 in the area adjacent spokes 90 of the drum12. If desired, side sealing means 92 may also be provided extendinginto the vat 16 in the opposite direction from the side skirts 82. The

6 side sealing ring 92 may extend peripherally about the entire drum 12,and may be formed of rubber, neoprene coated canvas inch thick or anysuitable material. It is preferably held in place by the bolt 36 betweenthe side skirts 82 and the filler piece 88.

Another means of holding the side skirt 82 and the side seal 92 is alsoshown in FIG. 5. Here an angle iron 94 is provided between the die 14and the drum 12. The side skirts 32' and the side seal 92 are anchoredto the angle iron via bolt $6.

The combined effect of the different elements of the apparatus disclosedherein provides optimum conditions for pulp deposition by providing aquiescent zone during th most important phases of molding and byreducing the tendency of lightly held gelatinous pulp to run downtowards the trailing edge of pulp molded objects. The invention thusprovides an improvement over [the invention of parent application SerialNo. 191,985 which is itself highly successful.

Although the invention shown is embodied in a preferred form, it isintended that the disclosure be ill-usrative trather than definitive. Itwill be obvious to those skilled in the ant that various changes may bemade without departing from the scope and spirit of the invention andtherefore the invention is not to be limited to what is shown in thedrawings and described in the specification, but only as indicated inthe appended claims.

What is claimed is:

1. In an apparatus for forming molded pulp articles comprising a slurryvat, an entrance into said vat, means communicating with said vat tofeed a pulp stock there.- to through said entrance to maintain the pulpslurry in substantial agitation and homogeneity, wall means forming aprimary chamber in said vat into which the pulp stock slurry isinitially introduced and a secondary chamher in proximity to andcommunication with said primary chamber, a suction die carrier mountedabove said vat and including at least one molding die thereon movable inone direction through said secondary chamber first downwardly and thenupwardly for receiving a pulp preform thereon, the improvementcomprising transversely extending wiper blade means disposed in trailingrelation to said molding die and contacting a portion of said wall meansas one molding die passes through said slurry in said vat, and vatdischarge means for passing said slurry out of said secondary chamber ata point slightly downstream and approximately adjacent the extremedownward position of said die.

2. A device in accordance with claim 1 wherein a portion of said wallmeans comprises a perforated false bottom separating said primary andsecondary chambers, and wherein a plurality of dies are mounted on saiddie carrier with said dies having leading and trailing wiper blades.

3. A device in accordance with claim 2 wherein said portion of said wallmeans which said wiper blades contact is the same portion comprisingsaid perforated false bottom, said false bottom having at least onesolid portion extending longitudinally a distance about equal to thedistance between wiper blades, said perforated false bottom beingapproximately equal in length to twice the distance between wiperblades, and said perforations consisting of a single transverse row ofapertures at about the longitudinal center of said false bottom.

4. A device in accordance with claim 3 further comprising a battle meansin said primary chamber adjacent said entrance means and wherein saidbafiie means and said entrance means lie below said transverse row ofapertures.

5. A device in accordance with claim 2 wherein said portion of said wallmeans which said wiper blade contacts is different from said portioncomprising said perforated false bottom, said perforated false bottombeing highly perforated and acting to break the force of slurry flowingfrom said primary chamber to said secondary chamber, and wherein saidwiper blade contacting wall portion is not substantially greater inlength than twice the distance between wiper blades, said wiper bladecontacting wall portion comprising a by-pass section extending beyondsaid wiper blades, said by-pass section extending transversely acrosssaid wiper blades contacting portion and being spaced a distance aboutequal to the distance between the wiper blades from the leading edge ofsaid wiper blade contacting wall portion.

6. A device in accordance with claim wherein the length of said wiperblade contacting wall portion is about equal to twice the distancebetween wiper blades and wherein said by-pass is located at about thelongitudinal center thereof.

7. A device in accordance with claim 5 further comprising bafile meansin said primary chamber adjacent said entrance means and wherein saidbafile means and said entrance means lie below said highly perforatedfalse bottom and said highly perforated false bottom is spacedhorizontally adjacent said wiper blade contacting wall portion.

8. A device in accordance with claim 5 wherein the length of said wiperblade contacting wall portions is less than twice the distance betweenwiper blades.

9. A device in accordance with claim 5 further comprising means toperiodically lengthen and shorten the length of said wiper bladecontacting wall portion to provide one period when said length is lessthan twice the distance between two wiper blades and another period whensaid length is substantially equal in length to twice the distancebetween two wiper blades.

10. A device in accordance with claim '7 further comprising laterallyextending dilution water jetting means in said vat wherein saidlaterally extending dilution water jetting means is positioned in saidprimary chamber between said balfle and said highly perforated falsebottom.

11. A device in accordance with claim 7 further comprising laterallyextending dilution water jetting means in said vat wherein saidlaterally extending dilution water jetting means is positioned in saidsecondary chamber between said highly perforated false bottom and theleading edge of said wiper blade contacting wall portion.

12. A device in accordance with claim 5 further comprising means toshield said dies from pulp during a portion of travel through said vat,said shielding means comprising a laterally extending plate positionedin said secondary chamber above said highly perforated false bottom andin contacting relation with the free ends of said wiper blades, saidplate being about equal in length to the distance between wiper blades,the leading edge of said shield plate being positioned above the stockslurry level in said vat and the trailing edge thereof being spaced adistance from the leading edge of said wiper blade contacting wallportion.

13. A device in accordance with claim 1 comprising side skirts extendingfrom said suction die carrier adjacent said die to prevent slurry fromflowing behind said die and also comprising side sealing means extendingparallel but in the opposite direction from said side skirts, and meansto attach said side skirts and said sealing means to said die carrier.

14. In an apparatus for forming molded pulp articles comprising a slurryvat, an entrance means into said vat, means communicating with said vatto feed a pulp stock thereto through said entrance to maintain the pulpslurry in substantial agitation and homogeneity, wall means forming aprimary chamber in said vat into which the pulp stock slurry isinitially introduced and a sec ondary chamber in proximity to andcommunicating with said primary chamber, a suction die calrier mountedabove said vat and including at least one molding die thereon movable inone direction through said secondary chamber first downwardly and thenupwardly for receiving a pulp preform thereon, the improvementcomprising transversely extending wiper blade means disposed in trailingrelation to said molding die and contacting a portion of said wall meansas said one molding die passes through said slurry in said vat, and vatdischarge means for passing said slurry out of said secondary chamber ata point downstream from the lowermost point of travel of said die wherethe weight of said slurry in said secondary chamber at said dischargemeans does not exceed the force of infeed of said slurry into saidsecondary chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,730,450 10/1929Chaplin 162-391 1,979,794 11/1934 Chaplin 162-183 2,000,085 5/1935Maginnis 162-392 2,925,863 2/1960 Chaplin 162-391 2,961,368 11/1960Lyons 162-390 2,995,187 8/1961 Wells 162-390 3,011,546 12/1961 Peppleret a1 162-390 3,043,742 7/1962 Chaplin 162-390 3,165,437 1/1965 Foote162-390 DONALL H. SYLVESTER, Primary Examiner.

14. IN AN APPARATUS FOR FORMING MOLDED PULP ARTICLES COMPRISING A SLURRYVAT, AN ENTRANCE MEANS INTO SAID VAT, MEANS COMMUNICATING WITH SAID VATTO FEED A PULP STOCK THERETO THROUGH SAID ENTRANCE TO MAINTAIN THE PULPSLURRY IN SUBSTANTIAL AGITATION AND HOMOGENEITY, WALL MEANS FORMING APRIMARY CHAMBER IN SAID VAT INTO WHICH THE PULP STOCK SLURRY ISINITIALLY INTRODUCED AND A SECONDARY CHAMBER IN PROXIMITY TO ANDCOMMUNICATING WITH SAID PRIMARY CHAMBER, A SUCTION DIE CARRIER MOUNTEDABOVE SAID VAT AND INCLUDING AT LEAST ONE MOLDING DIE THEREON MOVABLE INONE DIRECTION THROUGH SAID SECONDARY CHAMBER FIRST DOWNWARDLY AND THENUPWARDLY FOR RECEIVING A PULP PREFORM THEREON, THE IMPROVEMENTCOMPRISING